Conductivity control of semiconducting silicides by composition ratios and formation of homojunction solar cells on glass substrates

2020 Fiscal Year Annual Research Report

• Project/Area Number: 18H03767
• Research Institution: University of Tsukuba
• Principal Investigator: 末益 崇 筑波大学, 数理物質系, 教授 (40282339)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 太陽電池 / 界面層 / 蓄積 / 再結合

Outline of Annual Research Achievements

新しい太陽電池材料として期待されるバリウムシリサイド(BaSi2)は、禁制帯幅が太陽電池にふさわしい1.3eVであり、光吸収係数が大きいとの特徴をもつ。また、第一原理計算より、Si空孔が形成されやすく、光生成キャリアの再結合中心になることが分かっている。このような欠陥は、水素や伝導型制御に用いる不純物BやAs等を1cc当たり10の17乗程度の低濃度だけドーピングすることで不活性化できるため、この手法を用いて本年度はBaSi2ホモ接合太陽電池の高効率化に取り組んだ。しかし、変換効率が1%以下と小さいため、その原因を各層の複素誘電率を用いた光学シミュレーションにより探った。その結果、表面側のn-BaSi2エミッタ層で生じる光生成電子・ホール対の大部分が、外部回路に取り出せていないことが分かった。これは、BaSi2の光吸収係数が非常に大きいことが原因と考えられる。そのため、欠陥の入りやすい表面側での光吸収を抑える新しい太陽電池構造として、ワイドギャップn型半導体であるAZO(AlドープZnO)とp-BaSi2ヘテロ接合太陽電池を考案し、その太陽電池動作を初めて実証した。この構造では、ZnO/BaSi2ヘテロ界面での大きなバンド不連続に起因して、電子・ホール対がヘテロ界面の蓄積し、再結合する。そのため、BaSi2と同じ電子親和力(3.2eV)をもつ界面層を挿入することで、電子とホールを空間的に分離する必要がある。そのような界面層として、n-AZO/p-Cu2O太陽電池で実績のあるZnGeO層を見出し、シミュレーションではあるが、界面層の挿入により、太陽電池特性が大幅に改善できることが明らかになった。初期的な実験ながら、スパッタ法により、ZnGeO/BaSi2構造の形成にも成功した。

Research Progress Status

令和2年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和2年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] Universiti Kebangsaan Malaysia(マレーシア)
  • Country Name: MALAYSIA
  • Counterpart Institution: Universiti Kebangsaan Malaysia
• [Int'l Joint Research] Balarusian State Univ. Inf. Raidoelect.(ベラルーシ)
  • Country Name: BELARUS
  • Counterpart Institution: Balarusian State Univ. Inf. Raidoelect.
• [Int'l Joint Research] Delft University of Technology(オランダ)
  • Country Name: NETHERLANDS
  • Counterpart Institution: Delft University of Technology
• [Journal Article] Comparison of C doping technique between SiC and C targets for high-photoresponsivity BaSi2 films by radio-frequency sputtering (2021)
  • Author(s): Taira Nemoto, Ryota Koitabashi, Masami Mesuda, Kaoru Toko, Takashi Suemasu
  • Journal Title: Japanese Journal of Applied Physics Volume: 60 Pages: 058001.1-3
  • DOI: 10.35848/1347-4065/abf317
  • Peer Reviewed
• [Journal Article] Mechanisms of carrier lifetime enhancement and conductivity-type switching on hydrogen-incorporated arsenic-doped BaSi2 (2021)
  • Author(s): Sho Aonuki, Zhihao Xu, Yudai Yamashita, Kazuhiro Gotoh, Kaoru Toko, Noritaka Usami, Andrew B. Filonov, Siarhei A. Nikitsiuk, Dmitri B. Migas, Denis A. Shohonov, Takashi Suemasu
  • Journal Title: Thin Solid Films Volume: 724 Pages: 138629.1-7
  • DOI: 10.1016/j.tsf.2021.138629
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Effect of post-annealing on the significant photoresponsivity enhancement of BaSi2 epitaxial films on Si(111) (2021)
  • Author(s): Yurika Haku, Sho Aonuki, Yudai Yamashita, Kaoru Toko, Takashi Suemasu
  • Journal Title: Applied Physics Express Volume: 14 Pages: 021003.1-4
  • DOI: 10.35848/1882-0786/abdc9f
  • Peer Reviewed
• [Journal Article] Formation of high-photoresponsivity BaSi2 films on glass substrate by radio-frequency sputtering for solar cell applications (2021)
  • Author(s): Ryota Koitabashi, Taira Nemoto, Yudai Yamashita, Masami Mesuda, Kaoru Toko, Takashi Suemasu
  • Journal Title: Journal of Physics D: Applied Physics Volume: 54 Pages: 135106.1-6
  • DOI: 10.1088/1361-6463/abd434
  • Peer Reviewed
• [Journal Article] Solar cell operation of sputter-deposited n-BaSi2/p-Si heterojunction diodes and characterization of defects by deep-level transient spectroscopy (2021)
  • Author(s): Taira Nemoto, Sho Aonuki, Ryota Koitabashi, Yudai Yamashita, Masami Mesuda, Kaoru Toko and Takashi Suemasu
  • Journal Title: Applied Physics Express Volume: 14 Pages: 051010.1-5
  • DOI: 10.35848/1882-0786/abfb87
  • Peer Reviewed
• [Journal Article] Impact of radio-frequency power on the photoresponsivity enhancement of BaSi2 films formed by sputtering (2020)
  • Author(s): Taira Nemoto, Ryota Koitabashi, Masami Mesuda, Kaoru Toko, Takashi Suemasu
  • Journal Title: Applied Physics Express Volume: 13 Pages: 085511.1-4
  • DOI: 10.35848/1882-0786/aba9a1
  • Peer Reviewed
• [Journal Article] Fabrication of high-photoresponsivity BaSi2 films formed on conductive layers by radio-frequency sputtering (2020)
  • Author(s): Ryota Koitabashi, Taira Nemoto, Masami Mesuda, Kaoru Toko, Takashi Suemasu
  • Journal Title: Applied Physics Express Volume: 13 Pages: 975506.1-4
  • DOI: 10.35848/1882-0786/ab9622
  • Peer Reviewed
• [Journal Article] Atomic hydrogen passivation for photoresponsivity enhancement of boron-doped p-BaSi2 films and performance improvement of boron-doped p-BaSi2/n-Si heterojunction solar cells (2020)
  • Author(s): Zhihao Xu, Takuma Sato, Louise Benincasa, Yudai Yamashita, Tianguo Deng, Kazuhiro Gotoh, Kaoru Toko, Noritaka Usami, Andrew B. Filonov, Dmitri B. Migas, Denis A. Shohonov, Takashi Suemasu
  • Journal Title: Journal of Applied Physics Volume: 127 Pages: 233104.1-15
  • DOI: 10.1063/5.0005763
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Hydrogen states in hydrogen-passivated semiconducting barium disilicide measured via muon spin rotation (2020)
  • Author(s): Zhihao Xu, Takuma Sato, Jumpei Nakamura, Akihiro Koda, Koichiro Shimomura, Andrew B. Filonov, Dmitry B. Migas, Takashi Suemasu
  • Journal Title: Japanese Journal of Applied Physics Volume: 59 Pages: 071004.1-7
  • DOI: 10.35848/1347-4065/ab984b
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Significant enhancement of photoresponsivity in As-doped n-BaSi2 epitaxial films by atomic hydrogen passivation (2020)
  • Author(s): Sho Aonuki, Yudai Yamashita, Takuma Sato, Zhihao Xu, Kazuhiro Gotoh, Kaoru Toko, Yoshikazu Terai, Noritaka Usami, Takashi Suemasu
  • Journal Title: Applied Physics Express Volume: 13 Pages: 051001.1-4
  • DOI: 10.35848/1882-0786/ab8725
  • Peer Reviewed
• [Presentation] First Operation of n+-AZO/p-BaSi2 Thin Film Solar Cells (2020)
  • Author(s): Yudai Yamashita, Kaoru Toko, and Takashi Suemasu
  • Organizer: The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)
  • Int'l Joint Research
• [Presentation] Remarkable improvement of the optical properties of As-doped n-BaSi2 films (2020)
  • Author(s): Sho Aonuki, Kaoru Toko, and Takashi Suemasu
  • Organizer: The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)
  • Int'l Joint Research
• [Presentation] Formation of the high photoresponse BaSi2 films sputtered on glass substrates (2020)
  • Author(s): Ryota Koitabashi, Taira Nemoto, Masami Mesuda, Kaoru Toko, and Takashi Suemasu
  • Organizer: The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)
  • Int'l Joint Research
• [Presentation] 3D device simulation and first demonstration of BaSi2 thin film solar cells (2020)
  • Author(s): Yudai Yamashita, Rudi Santbergen, Carlos Mario Ruiz Tobon, Olindo Isabella, and Takashi Suemasu
  • Organizer: PRiME 2020
  • Int'l Joint Research
• [Presentation] Optical 3D device simulation of BaSi2 thin film solar cells (2020)
  • Author(s): Yudai Yamashita, Rudi Santbergen, Carlos Mario Ruiz Tobon, Miro Zeman, Olindo Isabella, and Takashi Suemasu
  • Organizer: 37th European PV Solar Energy Conference and Exhibition (37th EU-PVSEC)
  • Int'l Joint Research
• [Presentation] Hydrogen states in BaSi2 by muon spin rotation (2020)
  • Author(s): Zhihao Xu, Takuma Sato, Jumpei Nakamura, Akihiro Koda, Koichiro Shimomura, and Takashi Suemasu
  • Organizer: 37th European PV Solar Energy Conference and Exhibition (37th EU-PVSEC)
  • Int'l Joint Research
• [Presentation] Atomic hydrogen passivation for marked photoresponsivity improvement of As-doped n-BaSi2 films (2020)
  • Author(s): S. Aonuki, Y. Yamashita, T. Sato, Z. Xu, K. Toko, and T. Suemasu
  • Organizer: 62th Electric Materials Conference
  • Int'l Joint Research
• [Presentation] First demonstration of n+-AZO/p-BaSi2 thin film solar cells (2020)
  • Author(s): Yudai Yamashita, Kaoru Toko, and Takashi Suemasu
  • Organizer: Fifth Asian School-Conference on Physics and Technology of Nanostructured Materials (ASCO-NANOMAT 2020)
  • Int'l Joint Research
• [Remarks] 環境半導体・磁性体研究室
  • URL: http://www.bk.tsukuba.ac.jp/~ecology/